1. Field of the Invention
This invention relates to a radiation image recording and read-out apparatus for exposing a stimulable phosphor sheet to a radiation passing through an object to have a radiation image of the object stored thereon, exposing the stimulable phosphor sheet to stimulating rays which cause it to emit light in proportion to the stored radiation energy, and detecting the emitted light and converting it into an electric signal. This invention particularly relates to a radiation image recording and read-out apparatus in which the stimulable phosphor sheet is used repeatedly. This invention also relates to a radiation image storage panel for use in the radiation image recording and read-out apparatus, and a method of moving the radiation image storage panel.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. No. 4,258,264, 4,276,473, 4,315,318 and 4,387,428, and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet comprising the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet or simply as a sheet) is first exposed to a radiation passing through an object to have a radiation image stored thereon, and is then scanned with stimulating rays which cause it to emit light in proportion to the stored radiation energy. The light emitted by the stimulable phosphor sheet when the sheet is exposed to the stimulating rays is photoelectrically detected and converted into an electric image signal, which is processed as desired to reproduce a visible image having an improved image quality, particularly a high diagnostic efficiency and accuracy. The finally obtained visible image may be reproduced in the form of a hard copy or may be displayed on a cathode ray tube (CRT). In this radiation image recording and reproducing system, the stimulable phosphor sheet is used to temporarily store the radiation image in order to reproduce the final visible image therefrom on a final recording medium. For economical reasons, therefore, it is desirable that the stimulable phosphor sheet be used repeatedly.
Further, in a mobile X-ray diagnostic station such as a traveling X-ray diagnostic station in the form of a vehicle like a bus which is provided with a radiation image recording and read-out apparatus for use in the aforesaid radiation image recording and reproducing system and moves from place to place to record radiation images for mass medical examinations, it is disadvantageous to load the mobile X-ray diagnostic station with a large number of stimulable phosphor sheets, and the number of the stimulable phosphor sheets which can be loaded on the mobile X-ray diagnostic station is limited. Therefore, it is desired to load the mobile X-ray diagnostic station with stimulable phosphor sheets which can be used repeatedly, store the radiation images of the respective objects on the stimulable phosphor sheets, transfer the electric image signals read out from the stimulable phosphor sheets to a recording medium having a large storage capacity, such as a magnetic tape, and circulate and reuse the stimulable phosphor sheets for further image recording and read-out operations, thereby to obtain the radiation image signals of many objects. Further, when image recording is conducted continuously by circulating and reusing the stimulable phosphor sheets, it becomes possible to increase the image recording speed in mass medical examinations. This is very advantageous in practical use.
In order to reuse stimulable phosphor sheets as described above, the radiation energy remaining on the stimulable phosphor sheet after it is scanned with stimulating rays to read out the radiation image stored thereon should be erased by exposure to light or heat as described, for example, in U.S. Pat. No. 4,400,619 or Japanese Unexamined Patent Publication No. 56(1981)-12599. The stimulable phosphor sheet should then be used again for radiation image recording.
From the aforesaid viewpoint, the applicant proposed in Japanese Unexamined Patent Publication No. 59(1984)-192240 a built-in type radiation image recording and read-out apparatus comprising:
i. a circulation and conveyance means for conveying at least one stimulable phosphor sheet for recording a radiation image thereon along a predetermined circulation path,
ii. an image recording section positioned on said circulation path for recording a radiation image of an object on said stimulable phosphor sheet by exposing said stimulable phosphor sheet to a radiation passing through said object,
iii. an image read-out section positioned on said circulation path and provided with a stimulating ray source for emitting stimulating rays for scanning said stimulable phosphor sheet carrying said radiation image stored thereon at said image recording section, and a photoelectric read-out means for detecting light emitted by said stimulable phosphor sheet scanned with said stimulating rays to obtain an electric image signal, and
iv. an erasing section positioned on said circulation path for, prior to the next image recording on said stimulable phosphor sheet for which the image read-out has been conducted at said image read-out section, having said stimulable phosphor sheet release the radiation energy remaining on said stimulable phosphor sheet,
whereby said stimulable phosphor sheet is circulated through said image recording section, said image read-out section and said erasing section and reused for radiation image recording.
In the aforesaid radiation image recording and readout apparatus, recording and read-out of radiation images can be conducted continuously and efficiently.
However, the aforesaid radiation image recording and read-out apparatus has the drawback that, since the circulation path for the stimulable phosphor sheet is provided in the apparatus, the apparatus becomes large.